1. Field of the Invention
The present invention relates to implantable or insertable medical devices and more particularly to implantable or insertable medical devices comprising a polymer that releases a therapeutic agent.
2. Brief Description of the Background Art
Superoxide dismutase mimics are enzymes that catalyze dismutation of superoxide radicals (O2′−) by converting them to less reactive hydrogen peroxide (H2O2) and dioxygen (O2). The body's response to implanted biomedical materials typically involves inflammation to varying degrees. To address this inflammation, superoxide dismutase mimics have been covalently attached to the surfaces of various biomaterials for implantation. See Udipi, K. et al, “Modification of inflammatory response to implanted biomedical materials in vivo by surface bound superoxide dismutase mimics,” J. Biomed Mater. Res. 2000 Sep. 15; 51(4):549–60.
Local delivery of therapeutic agents from implantable or insertable medical devices is an important new technology in the treatment of diseases.
For example, intraluminal stents are commonly inserted into the coronary artery after percutaneous transluminal coronary angioplasty procedures. Such stents are provided to maintain the patency of the coronary artery by supporting the arterial walls and preventing abrupt reclosure or collapse thereof, which can occur after the angioplasty procedure. However, the presence of a stent can exacerbate restenosis of the vessel.
In response to this problem, local delivery of a number of restenosis-inhibiting therapeutic agents (such as paclitaxel, rapamycin, nitric oxide donors, and so forth) from coatings of stents that have been inserted after percutaneous transluminal coronary angioplasty procedures has been proposed.
However, the technology associated with drug delivery from coated vascular medical devices such as coronary stents is a relatively new one. Moreover, while numerous therapeutic agents have been proposed as noted above, it is possible that certain of these agents will ultimately be found to act on an inappropriate cell physiology, or that they are not be presented to the vasculature in appropriate concentrations.